This application is based on application No. 2000-66791 filed in the Korean Industrial Property Office on Nov. 10, 2000, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to a method for preparing acrylonitrile-butadiene-styrene (ABS) latex, and more particularly, to a method for preparing acrylonitrile-butadiene-styrene having high total solid content through emulsion polymerization of the styrene monomer in order to graft-copolymerize the styrene monomer.
(b) Description of the Related Art
Since an acrylonitrile-butadiene-styrene (ABS) resin has excellent characteristics such as impact resistance, chemical resistance, workability, and surface gloss, it is generally used in monitor housing, computer game-player housing, home appliances, and office machines, and as the use of the ABS resin is increasing, its production also needs to be increased. However, in order to increase the production volume of the ABS resin, it does not help that new equipment for its production is added to the existing facilities. In order to solve the said problem, it has been studied that the production volume of the ABS resin increases by shortening the processing time with a shorter reaction time, an increase in the rubber content of latex, a decrease in the rubber content of the final ABS injection molding products and extrusion products, or an increase in the total solid content of latex.
In particular, though the production volume of the ABS resin is capable of increasing by increasing the total solid content of latex in a lab test, the productivity decreases on real processes, because coagulated materials generates due to the shear stress of the stirrer, and time is needed to remove the film which is formed on the latex surface during its transportation or storage.
It is an object of the present invention to provide a method for preparing acrylonitrile-butadiene-styrene latex having a high total solid content.
It is another object to provide a method for preparing acrylonitrile-butadiene-styrene latex having a high total solid content, which is capable of increasing in the production volume by decreasing the amount of coagulated materials which are generated during graft-copolymerization, or the film which is formed on the latex surface.
These objects may be achieved by a preparation method of the acrylonitrile-butadiene-styrene having a high total solid content, which comprises a step of emulsion polymerization of:
i) polybutadiene rubber latex;
ii) an aromatic vinyl compound; and
iii) vinyl cyanide with the addition of a reactive emulsifier thereto.
In the following detailed description, only the preferred embodiment of the invention has been shown and described, simply by way of illustration of the best mode contemplated by the inventors of carrying out the invention. As will be realized, the invention is capable of modification in various obvious respects, all without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature, and not restrictive.
The acrylonitrile-butadiene-styrene latex of the present invention is prepared by the addition of an aromatic vinyl compound and a vinyl cyan compound to polybutadiene rubber latex, and emulsion copolymerization of the mixture with the addition of a reactive emulsifier, in order to decrease in the amount of coagulated materials which are generated during the emulsion copolymerization, and to prevent the film from being formed on the latex surface. Thus, the acrylonitrile-butadiene-styrene rubber latex has high productivity and total solid content of the latex.
In order to obtain the latex of the present invention, the acrylonitrile-butadiene-styrene latex is prepared by the emulsion compolymerization of:
i) 40 to 70 parts by weight of polybutadiene rubber latex;
ii) 15 to 30 parts by weight of aromatic vinyl compound; and
iii) 10 to 25 parts by weight of vinyl cyanide with the addition of 0.01 to 4.0 weight parts of reactive emulsifier thereto.
The polybutadiene rubber latex of i) is a rubber latex mixture comprising:
a) a large-diameter-polybutadiene rubber latex having a high gel content, which has a particle diameter ranging from 2600 to 5000 xc3x85 in an average diameter, the gel content ranging from 70 to 95%, and swelling index ranging from 12 to 30; and
b) a large-diameter-polybutadiene rubber latex having low gel content, which has a particle diameter ranging from 2600 to 5000 xc3x85 in an average diameter, the gel content ranging from 60 to 85%, and swelling index ranging from 18 to 40, and
more preferably, the large-diameter-polybutadiene rubber latex having high gel content of a) and large-diameter-polybutadiene rubber latex having low gel content of b) are mixed in a weight ratio of 10xcx9c50 to 50xcx9c10.
In order to perform the emulsion copolymerization efficiently, the aromatic vinyl compound and vinyl cyan compound are twice added to the mixture of rubber latex as monomers. In the first addition, 25 to 80 parts by weight of the monomers based on 100 parts by weight of the total monomers are added, and 75 to 20 parts by weight of the monomers, the remaining monomers, are added in the second addition.
That is, the acrylonitrile-butadiene-styrene latex is prepared by the steps comprising:
a) placing 40 to 70 parts by weight of the rubber latex mixture of i); 3.75 to 24 parts by weight of the aromatic vinyl compound monomer of ii); 2.5 to 20 parts by weight of the vinyl cyan compound monomer; and equal to or less than 4 parts by weight of the reactive emulsifier together in a reactor in order to react the materials first;
b) adding 6 to 26.25 parts by weight of the aromatic vinyl compound monomer of ii); 5 to 22.5 parts by weight of the vinyl cyan compound monomer of iii); and 0.01 to 4 parts by weight of the reactive emulsifier agent together or continuously to the materials of a) in order to react the mixture secondly, 30 to 90 minutes after the first reaction in the step a), and when the conversion ratio of monomers of ii) and iii) to polymers ranges from 40 to 90 wt %.
The reactive emulsifier of the present invention includes anionic emulsifiers comprising allyl, methacryloyl, and propenyl groups, or neutral emulsifier.
An exemplary anionic emulsifier agent comprising an allyl group includes sulfate of polyoxyethylene allylglycidyl nonylphenyl ether, and ADEKARIA SOAP SE based agents (a product by Asahi Denka Co.) which is suitable for a commercial market. The neutral emulsifier agent comprising an allyl group includes polyoxyethylene allylglycidyl nonylphenyl ether based emulsifiers, and ADEKARIA SOAP NE based emulsifier (a product by Asahi Denka Co.) which is suitable for a commercial market. The anionic emulsifier comprising (metha)acryloile group includes ELEMINOL RS based emulsifiers (a product by Sanyo kasei Co.), and the neutral emulsifier comprising the (metha)acryloile group includes RMA-560 based emulsifiers (a product by Nippon Surfactant Co.). An exemplary anionic emulsifier comprising the propenyl group includes polyoxyethylene nonyl propenyl ether ammonium sulfate, and AQUARON BC based emulsifiers (a product by Daiichi kogyo Seiyaku Co.) which is suitable for a commercial market. The reactive emulsifier of the present invention may be selected from the group consisting of the aforementioned agents, or may include a mixture of the aforementioned emulsifier and the non-reactive emulsifier.
Preferably, 0.01 to 4.0 parts by weight of the reactive emulsifier based on 100 parts by weights of the ABS is added to the reactive materials during emulsion copolymerization, and more preferably, equal to or less than 2 parts by weight of the reactive emulsifier is added. When equal to or more than 4.0 parts by weight of the reactive emulsifier is added, agglutination of the small-diameter-latex polymer may be bad, and when equal to or less than 2.0 parts by weight of the reactive emulsifier is added, few agglutination of the small-diameter-latex may be occurred.
It is preferable that 0.1 to 2.0 parts by weight of the non-reactive emulsifier is added to the reactive materials, and it may be one or more selected from the group consisting of alkylaryl sufonate, alkalimethylalkyl sulfate, sulfonated alkylester, soap, and alkali rosinate.
The acrylonitrile-butadiene-styrene latex is also prepared by adding a conventional molecular weight controller and an initiator that is used in emulsion copolymerization.
It is preferable that 0.2 to 1.0 parts by weight of the molecular controller is added during copolymerization, and the molecular weight controller includes tertiary dodecyl mercaptane preferably.
In addition, it is preferable that 0.05 to 0.5 parts by weight of the initiator is added during copolymerization, and the initiator includes the mixture of one or more peroxides selected from the group consisting of tertiary butyl hydro peroxide, cumenehydro peroxide, diisopropyl benzenehydro peroxide, and persulfate; and one or more reductants selected from the group consisting of sodiumadidehyde sulfoxylate, sodiumethylene diamine tetraacetate, ferrous sulfate, dextrose, sodium pyrroline, and sodium sulfite.
The emulsion polymerization of the present invention is preferably performed at a temperature ranging from 40 to 80xc2x0 C. for 2 to 7 hours.
Hereinafter, the large-diameter-polybutadiene rubber latex having high gel content and the large-diameter-polybutadiene rubber latex having low gel content will be mentioned.
The polybutadiene rubber latex of a) is preferably prepared by a step comprising the agglutination of a small-diameter-rubber latex polymer having an average diameter-rubber latex polymer with an average diameter ranging from 70 to 95%, and a swelling index ranging from 12 to 30 with an acetic acid.
The small-diameter rubber latex polymer is preferably prepared by the steps comprising:
a) placing 100 parts by weight of 1,3-butadiene; 1 to 4 parts by weight of the non-reactive emulsifier; 0.1 to 0.6 parts by weight of the initiator; 0.1 to 1.0 parts by weight of an electrolyte; 0.1 to 0.5 parts by weight of the molecular weight controller; and 90 to 130 parts by weight of ion-exchange water all together in a reactor in order to react the reactants at a temperature ranging from 50 to 65xc2x0 C. for 7 to 12 hours; and
b) adding 0.05 to 1.2 parts by weight of the molecular weight controller to the reactants of a) in order to react the reactants at the temperature ranging from 55 to 70xc2x0 C. for 5 to 15 hours.
In addition, the large-diameter-polybutadiene rubber latex having low content of gel of i) b) is preferably prepared by the steps comprising:
a) placing 50 to 100 parts by weight of conjugated diene compound monomer; 1 to 4 parts by weight of non-reactive emulsifier; 0.2 to 1.5 parts by weight of the initiator; 0.5 to 2 parts by weight of an electrolyte; 0.1 to 0.5 parts by weight of the molecular weight controller; and 75 to 100 parts by weight of the ion-exchange water all together in a reactor in order to react the reactants at a temperature ranging from 65 to 75xc2x0 C. for 4 to 15 hours;
b) adding the rest of the conjugated diene compound monomer; and 0.1 to 1.0 parts by weight of the molecular weight controller all together or continuously to the reactants in order to react further the mixture at a temperature ranging from 70 to 85xc2x0 C. for 10 to 20 hours;
c) adding 0.01 to 3.0 parts by weight of the reactive emulsifier agent to the mixture, when the conversion of monomer to polymer due to the reaction in the step b) ranges from 30 to 70 wt %; and
d) adding a prohibitor to the resulting material in order to complete the polymerization reaction, when the conversion of monomer to polymer due to the reaction in the step c) ranges from 80 to 95 wt %.
The non-reactive emulsifier which is used for the preparation of the large-diameter-polybutadiene latex having high gel content, the small-diameter-polybutadiene latex having high gel content, and the polybutadiene latex having low gel content may include one or more selected from the group consisting of alkylaryl sulfonate, alkalimethyl alkyl sulfate, sulfonated alkylester, fatty acid soap, and alkali rosinate.
The initiator includes one or more selected from the group consisting of water-soluble persulfate such as sodium persulfate and potassium persulfate; fat-soluble initiator such as cumenehydro peroxide, diisopropyl benzenhydro peroxide, azobis isobutylnitrile, tertiary butylhydro peroxide, p-methanehydro peroxide, and benzoylperoxide; and redox systematic initiator.
The electrolyte includes one or more selected from the group consisting of KCl, NaCl, KHCO3, NaHCO3, K2CO3, Na2CO3, NaHSO3, K4P2O7, K3PO4, Na3PO4, K2HPO4, and Na2HPO4.
The molecular weight controller includes one or more selected from the group consisting of n-octylmercaptane (NOM), n-dodecylmercaptane (DDM), and t-dodecyl mercaptane (TDDM).
The reactive emulsifier which is used for the preparation of the large-diameter-polybutadiene rubber latex having low gel content includes the emulsifier which is used for preparation of the acrylonitrile-butadiene-styrene latex, as aforementioned.
The acrylonitrile-butadiene-styrene latex which is prepared from the emulsion copolymerization is coagulated with a flocculant such as sulfuric acid, MgSO4, CaCl2, and Al2(SO4) in order to obtain a resulting powder. The amount of the solid powder which is coagulated during the reaction is calculated as the equation 1 below, and the formation amount of the film is the film amount which is formed after being allowed to stand for 24 hours.
Amount of the coagulated material (%)=(the amount of the coagulated material formed in a reactor (g)/the total amount of the rubber and the monomer (g))xc3x97100xe2x80x83xe2x80x83[Equation 1]